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<document>

  <properties>
    <title>BCEL FAQ</title>
  </properties> 

  <body>

  <section name="FAQ">
    <p>
      <b>Q: </b>How can I ... with BCEL?
      <br/>
      <b>A: </b>Take a look at
      <tt>org.apache.bcel.util.BCELifier</tt>, it takes a given class
      and converts it to a BCEL program (in Java, of course). It will
      show you how certain code is generated using BCEL.
    </p>

    <p>
      <b>Q: </b> Is the BCEL thread-safe?
      <br/>
      <b>A: </b>BCEL was (deliberately) not designed for thread
      safety. See <a href="http://java.sun.com/docs/books/cp/">
      "Concurrent Programming in Java"</a>, by Doug Lea,
      for an excellent reference on how to build thread-safe wrappers.
    </p>

    <p>
      <b>Q: </b> Can I use BCEL in a commercial product?
      <br/>
      <b>A: </b> Yes, this is covered by the <a
      href="http://www.apache.org/licenses/">Apache License</a>, if you add a note about the original
      author and where to find the sources, i.e., 
      <a href="http://commons.apache.org/bcel/">http://commons.apache.org/bcel/</a>
    </p>

    <p>
      <b>Q: </b> (Typically for users of Xalan (XSLTC)) I'm getting
      <pre>
      ClassGenException: Branch target offset too large for short
      </pre>
      when compiling large files.
      <br/>

      <b>A: </b> The answer lies in internal limitations of the JVM,
      branch instruction like goto can not address offsets larger than
      a short integer, i.e. offsets >= 32767.<br/>
      The solution is to split the branch into in intermediate hops,
      which the XSLTC obviously doesn't take care off.
      (In fact you could replace gotos with the goto_w instruction,
      but this wouldn't help in the other cases).
    </p>

    <p>
      <b>Q:</b> Can I create or modify classes dynamically with BCEL?
      <br/>
      <b>A:</b> BCEL contains useful classes in the
      <tt>util</tt> package, namely <tt>ClassLoader</tt> and
       <tt>JavaWrapper</tt>. Take a look at the <tt> ProxyCreator</tt> example.
    </p>

    <p>
      <b>Q:</b> I get a verification error, what can I do?
      <br/>
      <b>A:</b> Use the JustIce verifier that comes together with BCEL
      to get more detailed information:
       <pre>
       java org.apache.bcel.verifier.Verifier &lt;your class&gt;</pre>
    </p>
    
    </section>
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